Bicycle with compliant seat post interface

ABSTRACT

A bicycle comprises front and rear wheels, a frame, a seat post, and a damping member. An upper portion of the seat post is movable relative to the frame between a first position and a second position. The damping member couples the seat post to the frame to dampen movement of the upper portion of the seat post. The damping member can be positioned at least partially in a top tube of the frame. Preferably, the seat post flexes when the upper portion of the seat post moves. The frame further includes a securing location for securing the seat post, and the securing location is a distance from the upper end of the seat tube that is at least 30% of a length of a seat tube. The seat post has a front-to-rear width, and the seat tube has a rear wall spaced from the seat post by a gap that is at least 25% of a front-to-rear width of the seat post.

BACKGROUND

The present invention relates generally to bicycles and specifically tobicycle frames having features for reducing the amount of road shocktransmitted to the rider.

Bicycles designed for paved roads commonly have a rigidly mounted rearwheel, which is light weight and provides rear end stiffness that isdesired by most serious road cyclists. In some riding conditions, suchas when riding long distances or over rough roads, it would be desirableto reduce the amount of shock or vibration transmitted from the road tothe rider. One way to accomplish this is to make the rear end of thebicycle compliant, which facilitates absorbing of the shock andvibration. However, such attempts to make the rear end of a road bikecompliant have commonly resulted in an increase in weight or loss ofrear end lateral stiffness, both of which are undesired.

SUMMARY

The present invention provides a bicycle comprising front and rearwheels, a frame supported on the front and rear wheels, a seat postsupported by the frame, and a damping member. An upper portion of theseat post is movable relative to the frame between a static firstposition and a stressed second position. The damping member (e.g., ahydraulic damper) couples the seat post to the frame to dampen movementof the upper portion of the seat post between the first and secondpositions. A collar can be used to secure the damping member to the seatpost. The damping member can be positioned at least partially in a tubeof the frame, such as the top tube. Preferably, a lower portion of theseat post is substantially rigidly secured to the frame, and the seatpost flexes when the upper portion of the seat post moves from the firstposition to the second position.

In one embodiment, the frame includes a seat tube having a lengthbetween a crank axis and an upper end of the seat tube, and the framefurther includes a securing location for securing the seat post. In thisembodiment, the securing location can be a distance from the upper endthat is at least 30% (preferably at least 45% and more preferably atleast 55%) of the length of the seat tube.

In another embodiment, the seat post has a front-to-rear width, and theframe includes a seat tube having a rear wall spaced from the seat postby a gap that is at least 25% (preferably at least 35% and morepreferably at least 45%) of the front-to-rear width of the seat post.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a bicycle embodying the present invention.

FIG. 2 is a front perspective view of a frame and seat post assemblyfrom the bicycle of FIG. 1.

FIG. 3 is a rear perspective view of the frame and seat post assembly ofFIG. 2.

FIG. 4 is an enlarged exploded view of the frame and seat post assemblyof FIG. 3.

FIG. 5 is a section view of the frame and seat post assembly taken alongline 5-5 in FIG. 2 with the seat post in an unflexed position.

FIG. 6 is the section view of FIG. 5 with the seat post in a flexedposition.

FIG. 7 is an enlarged view of a seat post binder clamp from the bicycleof FIG. 1.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

DETAILED DESCRIPTION

FIG. 1 illustrates a bicycle 10 having two wheels 12, a frame 14supported on the wheels 12, handlebars 16 for steering the bicycle 10,and a seat 18 for supporting the rider. The illustrated frame 14includes a top tube 20, a down tube 22, a seat tube 24, two chainstays26, and two seatstays 28, as is known in the art. A crankset 30 definesa crank axis 32 and supports two pedals 33. A seat post 34 is partiallypositioned inside the seat tube 24 and protrudes upwardly from the seattube 24 to support the seat 18.

Referring to FIGS. 2-6, the seat post 34 is secured to the seat tube 24by clamping at a clamping location 38 spaced from the upper end 36 ofthe seat tube 24 by a distance D that is about 60% of the length L ofthe seat tube (measured from the top of the seat tube to the crank axis32). For example, for a frame having a seat tube length L of 560 mm, thedistance D would be about 336 mm. The upper end 36 of the seat tube 24includes a flared portion 44 that defines a gap G between a rear wall 46of the flared portion 44 and the seat post 34. The illustrated gap isabout 50% of the front/rear width W of the seat post 34. For example,for a seat post having a width of 27.2 mm, the gap would be about 13.6mm. The opposing side walls 48 and front wall 50 of the flared portion44 are substantially parallel to each other and define a much smallergap between the walls 48,50 and the seat post 34.

By virtue of the above-described flared portion 44 and gap G, the upperend of the seat post 34 can move (e.g., flex) rearwardly and downwardlyto facilitate the absorption of shock and vibration travelling from therear wheel 12 and through the seatstays 28. The rearward and downwardflexing of the seat post is best shown in FIG. 5-6. It should beappreciated that instead of flexing the seat post could be designed topivot or hinge relative to the frame. In such an embodiment, a biasingmember would need to be used to bias the seat post toward the raised orunstressed position.

The illustrated arrangement further includes a damping member 52operatively positioned between the seat post 34 and the frame 14. Morespecifically, the damping member 52 is secured between the top tube 20and a collar 54 secured to the seat post 34, and is chosen to dampenmovement of the seat post 34 between the unflexed and flexed positions.The illustrated damping member 52 is an oil-filled through shaft damperwith a low speed rebound adjuster. It has bushings at each end of theouter tube so it can take side load from the seat post and it has aclevis mounting. Due to the close fit of the end bushings, the damperprovides lateral stability to the seat post.

The illustrated arrangement further includes a resilient boot 56positioned to cover the top opening of the seat tube 24, andparticularly the gap G between the seat post 34 and the flared portion44 of the seat tube 24. The boot 54 is made from a suitable elastomericmaterial, such as silicone. The boot 54 substantially fills the spacebetween the seat post and the upper end of the seat tube 24, therebyprevent intrusion of unwanted substances, such as water or dirt.

It is envisioned that different riders might want different stiffnessesfor the seat post (e.g., due to rider weight, riding style, or otherpreference). In this regard, the present invention allows the seat postto be customized to the rider's preference by changing the material,thickness, shape, or other relevant characteristic to achieve a seatpost with the desired dynamic performance. In addition, in analternative embodiment, the gap G between the seat post 34 and theflared portion 44 could be filled with a resilient bushing (not shown)to provide extra support to the seat post and resistance to flexing. Inthis embodiment, in the event that a rider perceives that the seat post34 is flexing too little or too much, the bushing can be replaced with asofter or stiffer bushing to achieve the desired amount of flexing ofthe seat post 34.

Referring to FIG. 7, clamping the seat post 34 to the seat tube 24 isaccomplished with a binder clamp including two ears 60 on opposing sidesof a slot 62 in the seat tube 24. A fastener 64 can be inserted throughone of the ears and threaded into the other to provide binding force toclamp the lower end of the seat post 34.

Various features and advantages of the invention are set forth in thefollowing claims.

1. A bicycle comprising: front and rear wheels; a frame supported on thefront and rear wheels; a seat post supported by the frame, an upperportion of the seat post being movable relative to the frame between astatic first position and a stressed second position; and a dampingmember coupling the seat post to the frame to dampen movement of theupper portion of the seat post between the first and second positions.2. A bicycle as claimed in claim 1, wherein a lower portion of the seatpost is substantially rigidly secured to the frame, and wherein the seatpost flexes when the upper portion of the seat post moves from the firstposition to the second position.
 3. A bicycle as claimed in claim 1,wherein the frame includes a crank axis and a seat tube having an upperend, wherein the seat tube has a length between the crank axis and theupper end, wherein the frame further includes a securing location forsecuring the seat post, and wherein the securing location is a distancefrom the upper end that is at least 30% of the length of the seat tube.4. A bicycle as claimed in claim 3, the distance from the upper end isat least 45% of the length of the seat tube.
 5. A bicycle as claimed inclaim 1, wherein the damping member includes a collar secured to theseat post.
 6. A bicycle as claimed in claim 1, wherein the dampingmember comprises a hydraulic damper.
 7. A bicycle as claimed in claim 1,wherein the damping member is positioned at least partially in a tube ofthe frame.
 8. A bicycle as claimed in claim 1, wherein the frameincludes a top tube, and wherein the damping member is positioned atleast partially in the top tube.
 9. A bicycle as claimed in claim 1,wherein the seat post has a front-to-rear width, and wherein the frameincludes a seat tube having a rear wall spaced from the seat post by agap that is at least 25% of the front-to-rear width of the seat post.10. A bicycle as claimed in claim 9, wherein the gap is at least 35% ofthe front-to-rear width of the seat post.
 11. A bicycle comprising:front and rear wheels; a frame supported on the front and rear wheels,the frame including a crank axis and a seat tube having an upper end,wherein the seat tube has a length between the crank axis and the upperend; and a seat post supported by the frame, an upper portion of theseat post being movable relative to the frame between a static firstposition and a stressed second position; wherein the frame furtherincludes a securing location for securing a lower portion of the seatpost, and wherein the securing location is a distance from the upper endthat is at least 30% of the length of the seat tube.
 12. A bicycle asclaimed in claim 3, the distance from the upper end is at least 45% ofthe length of the seat tube.
 13. A bicycle as claimed in claim 3, thedistance from the upper end is at least 55% of the length of the seattube.
 14. A bicycle as claimed in claim 1, wherein the lower portion ofthe seat post is substantially rigidly secured to the frame at thesecuring location.
 15. A bicycle as claimed in claim 1, furthercomprising a damping member coupling the seat post to the frame todampen movement of the upper portion of the seat post between the firstand second positions.
 16. A bicycle as claimed in claim 15, wherein thedamping member includes a collar secured to the seat post.
 17. A bicycleas claimed in claim 15, wherein the damping member comprises a hydraulicdamper.
 18. A bicycle as claimed in claim 15, wherein the damping memberis positioned at least partially in a tube of the frame.
 19. A bicycleas claimed in claim 15, wherein the frame includes a top tube, andwherein the damping member is positioned at least partially in the toptube.